Process of precipitating and separating metals from solution.



'nnsllmwwest c. ROBINSON."

PROCESS OF PR EClPlTATlNG AND SEPARATING ME-TALS FROM SOLUTION.

APPLICATION man SEPT. 12, 19:2.

Patented Oct. 12, 1915.

. .7 gmM/bow AM/ WA am a 1 '0 all whom it may concern.

ROBERT TOWNE, OF NEW YORK, AND CYRUS ROBINSON, 0F MOUNT VERNON, NEW YORK, ASSIGNORS TO METALLURGICAL ENGINEERING & PROCESS CORPORATION, A

CORPORATION OF, NEW YORK.

PROCESS PRECIIEITATING AND SEIE'ARATING -MET.ALS FROM SOLUTION.

Speeification of Letters Patent;

Application filed September 12, 1912. Serial No. 720,019.

Be it known that we, ROBERT S. TowNE, a citizen of the United States, residing at New York, in the county and State of New York, and CYnUs ROBINSON, a subject of the King of England, residing at Mount Vernon, in the county of lVestchester and State of New York, have invented certain new and useful Improvements in Processes of Precipitating and Separating Metals from Solution, of. which the following is a specification, reference being had to the accompanying drawing. v

This invention relates to a process for precipitating metals from solutions. For purposes of illustration we will in the following specification refer to the precipita tion of gold or silver from cyanid solutions by means of zinc as a precipitant. However, we desire it to be understood that our invention is not so limited but may under the proper conditions be used to effect the precipitation of gold and silver or other metals from other solutions, as for instance,

'a solution of sodium hyposul-fite. by means of other precipitants, as for instance, copper. The principal object of our invention is to provide a process by means of which the precipitant may be economically used in powdered orfinely divided form.

Further objects will be apparent from the following specification. I

In the accompanying drawings we have shown, more or less diagrammatically, one form of apparatus which may be used in the practice of our improved process, but we desire it to be understood that our invention is not limited to use in connection with the particular apparatus illustrated but may be practised in connection with any apparatus which is suitable.

Of the drawings-F'gure 1 is a side elevation, partly in cross section. 2 is a plan view.

Referring to the drawings, 1 represents a reservoir or clarifier to which, through the pipe or trough 2, can be supplied the cyanid or other solution carrying the dissolved gold, silver, or other metals to be recovered. This reservoir or clarifier 1 is preferably sufficiently large to permit the removal from the solution by sedimentation of any impurities which may be suspended in it.

Leading from the reservoir or clarifier 1 is a conduit 3 which preferably has a considerable length. The exact length in any particular case may be determined from a consideration of the kind of solution, the quantity'of values to be recovered and other conditions of use. In order to obtain the necessary length in a given 'space it may frequently be desirable to arrange the conduit in zigzag manner, as indicated. The conduit 3 is preferably a closed pipe ,as

shown in the drawings, but under certain Patented Oct. 12, 1915.

conditions it may be possible to use an open trough. D

At i we have indicated a device for feed.- ing to the solution in the conduit 3 regulated. quantities of precipitant. If a cyanid solution is being treated the precipitant is preferably zinc in powdered or finely divided form, The device 4 shown in the drawing is simply a funnel communicating at its lower end with the conduit; but it will beunderstood that other feeding devices suchas are now well known may be used.

In practice, the solution flows in a steady stream through the conduit 3 and the precipitant is steadily supplied to the stream from the feeder I. The movement of the solution and the precipitant through the conduit serves to commingle and agitate them with the result that at the end of the conduit all of the dissolved values have been precipitated and are being carried along in suspension.

The conduit 3 communicates at its end with the lower part of a settling tank or receptacle 5, which is preferably provided with an inverted conical oi pyramidal bottom at the apex of which there is connected a pipe 6 having a valve 7. As the solution with the suspended values enters the receptacle 5' and comes substantially to rest, the

values separate out by gravity and fall to the bottom where they can be removed through the pipe 6 and the'valve 7 either c'ontinuouslyor periodically. The solution freed from the precipitatedvalues moves slowly upward through the receptacle and is finally discharged into the troi'igh or launder through which it, can be led tobe used again.

' zinc have two functions. One is to mechani- Ye have, found that when there is unobstructed coi 'nnunication between the lower and upper parts of the receptacle and when the solution is permitted to flow freely from the upper part there isa decided tendency for a part of the more finely divided values to he carried upward and out with the solu-.

tion. The upward moving solution tends to carry some of the values, but amuch greater factor is the gas which is formed at the bottom of the receptacle probably by galvanic action between the'zinc and the silver. This gas passes rapidly upward throughthe receptacle and carries with it large quantities" of the precipitate. the res'ultbeing that the precipitate thus carried-upward is left in suspension near the top ofthe receptacle place a layer of zinclO in relatively finely divided form. The screen and the layer of cally: free the metallic values from the upward moving gas, and the other is to prevent the escape of' any of the valuesin solu-' tion in case they may have been re-dissolved during the movement upward through thereceptacle 5.

Around the upper part of' the receptacle there are provided a series of openings 11, 11 which communicate at their outer'en'tls with a trough 12 which extends around the receptacle and (:lischarges, into thetrough S;

Preferably we provide in front of the openings 11 11 a filteringinedium 13 which may if desired be formed of canvas. Through this filtering medium allof the liquid must pass before it canescape from the receptacle, and the medium therefore serves to catch any-values which may haveescaped the action of the screen 9 and the zinc layer 1O.

From the foregoing description it will be seen that our process involves the movement of the precipitated values in a general downward direction from the end of the conduit 3 and the movement ofthe solution in a. general upwarddirection from the end of the conduit. This prompt and rapid separation of the Values from the solution is of the utmost importance. In all earlier proces es in which use was made of finely divided'metallic precipitants the effort has been made to separate the (precipitated values from the solution by means of. a filter press or other device in which the values and the solution are carried along together in' the samedirection, the separation being {affected merely by mechanically retarding the movement et the 'alu'es with respect to that ofthe solution.

But these earlier processes have all been.

open to the very serious objection that there 'was a strong tendency for thevalues to he re-dissolved by the solution during the pe- 11()(l of separation. It has heretofore been commonly practised to use a (p antity of 'zinc or other metallic precipitant far in excess of that theoreticallynecessary for precipitation inorder to'insure the presence in the filter or otherseparating device of aii excess of zinc or othei" piecipitant to prevent the i-e-dissolving of the values.

.fact, in many cases it has been found necessary to use as much as eight times the amount'of Z1110 which would theoretically be necessary, and this has been found to be prohibitively expensive. Vith our .proc'ess,,by

quickly separating the alues from the solution weare able to very materially reduce the quantity of precipitant which itis necessary to initially use. The relatively large body of precipitant at 10' serves toprevent the escape of. any alues in the case of their becoming dissolved in the solution within the receptacle.

Ye providefor. a continuous stream of solution flowing along .tlie'prolonged Junbroke'n pathway provided by the pipe 3 and ,discharging directly-and without the breaking ofits' continuity into the fluid body in the tank 1. Preferably. the streamfiowing through the pipe 3 originates inan initial relatively large solution body. such as that contained in the tank 1 There is. therefore, acontinuity of solution fluid from the initial end of the pipe. 3, and preferably from the solution in the tank 1. .to the liquid in the tank 5. The stream through the pipe 3 never loses its velocity until the tank reached and theagitating and mixing ot the precipitant is continuously carried on. Furthermore, there is no opportunity for any of the precipitates to be. deposited-along the pipe, as the continued flow of liquit keeps them in suspension.

What we claim is:

1. The herein described process of pre to effect mixing. agitating,dissolving and.

precipitating, forming a stationary liquid body of approximately predetermined volume relatively elongated vertically and having at its bottom a relatively large region of quiescence and at its top a relativelylarge region for dissolving and precipitating, causing the aforesaid stream while maintaining its cont nu ty to flowinto the said fluid body at an intermediate level above the said region of quiescence and below the said region of dissolvingsand precipitating, causing the precipitated values to settle by gravity downward through the liquid body, removing the said Values at the lower part of the liquid body, causing the solution liquid to pass upward through the liquid, body away from the points of feeding'to effect continued-dissolving and precipitating, and discharging the solution liquid at the top of the said liquid body:

2. The herein described processo-f precipitating and separating dissolved values from a solution, which consists in causing a continuous stream of the solution of uniform cross area throughout to flow along a prolonged unbroken inclosed pathway, mingling with the stream of solution while thus flowing a precipitant in finely divided form to effect mixing, agitating, dissolving and precipitating, forming a stationary liquid body of approximately predetermined volume relatively elongated vertically and having at its bottom a relatively large region of quiescence and at its top a relatively large region for. dissolving and precipitating,'

causing the aforesaid'stream while maintaining its continuity to flow into the said fluid body at an intermediate level above the said region of quiescence and below the said region of dissolving and precipitating, causing the precipitated values to settle by gravity downwardthrough theliquid body,

removing the said values at thelower part of the liquid body, causing the solution liquid to pass upward through the liquid body away from the points of feeding to effect continued dissolving and precipitating, and discharging the solution liquid at the top of the said liquid body.

3. The herein described process of precipitating and separating dissolved values from a solution, which consists in forming a relatively large body of the solution, causing a continuous stream of the solution to flow from the said lqody along a prolonged unbroken pathway," mlnglmg w th the stream liquid body, removing the said values. at the lower part of the liquid body, causing the solution liquid to pass upward through thevolume at a point above the bottom to providea relatively large region of quiescence at the bottom, and at. the top a region for the final escape of the fluid, causlng the 'values after precipitating to settle by gravity downward through the said body of liquid and removing them from the quiescent lower "part thereof, causing the solution fluid to pass upward away from the points of feeding to elevated planes of discharge, and subjecting the solution to a filtering action at points adjacent the points of discharge and uniformly distributed horizontally over the entire cross area of the body of liquid.

5. The herein described process of precipitating and separating dissolved values from a solution, which consists in mingling with the solution a precipitant in finely divided form to effect precipitation, causing the solution and precipitant to flow along an extended pathway to permit prolonged mixing, agitating, dissolvingand precipitating, forming of the fluid a stationary body of approximately predetermined volume relatively elongated vertically, and having at the bottom a relatively large region of quiescence, and at the top region for the continu ance of the dissolving and precipitatingaction, supplying a stream of the fluid with the aforesaid contents to the aforesaid relatively stationary volume, causing the precipitated values to settle by gravity downward through the body of liquid, removing thesaid values at the lower part of the liquid body, causingv theso-lution fluid to pass upward away from the points of feeding to a point of discharge, and subjecting the solution fluid to the action of a body of precipitant before it reaches the said point of' discharge.

6. The herein-described process of sepa-i rating dissolved values from a solution containing a precipitant, it consisting in forming a relatively stationary vertically elongated body of approximately predetermined volume of said fluid, supplying a stream of the fluid to the said relatively stationary volume at a point above the bottom to provide a relativelylarge region of quiescence at the bottom, and at the top a region for the final escape of the fluid, causing the values after precipitating to settle by gravity downward'through the said body of liquid and removing them from the quiescent lower &" 1,156,383

part thereof, causing thesolution fluid to In testimony whereof e aifix out signapass upward away from the points of feedtures, in presence of two Witnesses.

ingto elevated planes of dischar 'e subjecting the solution to the action of a body of precipitant before it reaches the. points of discharge, and subjecting the solution to'a itnesses: I filtermg action at points adjacent 17116821101 FRED M. HILLIARD, points of discharge. I v j V. A. GILLESBY. 

